From before, to a game machine for business use, which allows a user to play games with charge, applied is the payment method that the user is required the payment of game-play fee by coins (real currency), A credit number is issued depending on the number of coins inputted by the user, and monetary value corresponding to the game-play fee is collected from the user by making the user consume the credits. Namely, the consumption of game-play fee is generally managed by replacing the game-play fee with a value in the unit system where a value for one unit is bigger than a value for the minimum unit of the currency. In recent years, in addition to such payment method with cash, proposed is a game system for business use, which enables a payment of the game-play with virtual money (for example, see the patent documents 1 to 3). The monetary value means a value corresponding to the fee which is quantified in accordance with the currency unit. For example, if one piece of JPY 100 coin is replaced with one credit, the one credit has the monetary value of JPY 100.
Patent Literature: PTL1: JP-A-2008-257518, PTL2: JP-A-2007-79643 and PTL3: JP-A-2006-94877.